HBase Region Assigner

During the course of normal HBase operation, table regions will occasionally become unassigned when regions are transitioned from one regionserver to another. As long a region remains unassigned, the data contained therein will be inaccessible. While reassigning an unassigned region is not difficult (assign regionName via hbase shell), HBase will not assign these wayward regions automatically. This can result in late-night pages and grumpy engineers.

In an effort to combat grumpiness, we created this application, which will run region assignment checks on every enabled HBase table on a scheduled basis. If any unassigned regions are encountered, we will instruct HBase to assign them to a regionserver.

Requirements

Java 8 or higher is required.

Development

This application is built using Gradle and Spring Boot. To build and run this application from source, clone the repository and run:

./gradlew bootRun -Dhbase.zookeeper-hosts=<comma-delimited list of hostnames> -Dhbase.zoo-keeper-port=<zk port>

Deployment / Installation

The application can be packaged into an executable jar by running ./gradlew bootJar. The resulting jar file can be found in build/lib. The jar can then be run via

java -jar path/to/jar.jar

or, on most Linux systems, an init.d or systemd service can be created.

Configuration

By default, the application will look for an application.properties file in /etc/hbase-assigner. This location can be changed by adding the following command line option when starting the application: spring.config.additional-location=/path/to/config. The properties file should follow standard properties file formatting.

Configuration Parameters

These parameters can be located in the application.properties file described above, or they can be passed as command line parameters (-D<name>=<value>).

Name	Description	Required?	Default
hbase.zookeeper-hosts	A comma-delimited list of Zookeeper hosts. These should be the same hosts which manage your HBase cluster.	yes	N/A
hbase.zookeeper-port	The port on which Zookeeper listens on the configured hosts.	yes	N/A
hbase.cron	A Quartz-style cron expression which will determine the frequency of automated region assignment checks.	no	0 */30 * * * * (every 30 minutes)
slack.url	A Slack incoming webhook URL which will be used for report publication. If unconfigured, Slack publication will be disabled.	no	none
slack.channel	The name of the Slack channel to which the reports will be published. If unconfigured, Slack publication will be disabled.	no	none
server.port	Port on which the application will listen for incoming HTTP requests.	no	8080

REST API

For the most part, the region assigner is intended to run its scheduled checks in the background, report on its activity, and otherwise be left alone. There are, however, several convenient REST endpoints available:

Path	Method	Description
/api/hbase/_check-regions	POST	Runs a region check on all enabled HBase tables. The results of the check are returned in JSON form, but are not published to Slack.
/api/hbase/_check-regions/{table}	POST	Runs a region check only on the given table.
/api/hbase/servers	GET	Returns a list of the currently available HBase servers.
/api/hbase/servers/{server}	GET	Returns details regarding the server running on the given host.
/api/hbase/servers/{server}/regions	GET	Retrieves information regarding all of the regions which are assigned to the given server.
/api/hbase/master	GET	Basic information about the current HBase master.
/api/hbase/tables	GET	A listing of all existing HBase tables.
/api/hbase/tables/{table}/	GET	Details regarding the table with the given name.
/api/hbase/tables/{table}/regions	GET	A listing of the regions belonging to the given table.